Many facilities and buildings like museums, archives, clean rooms, data centers, or pharmaceutical labs require tight control on air quality (dust and gaseous contamination). Extensive effort is devoted to reduce air contamination and maintain safe operating conditions. Atmospheric contamination is known to exhibit geographical and temporal variations since it is closely tied to local human pollution activities such as power production, agriculture, transport, etc. To overcome atmospheric pollution in the above mentioned facilities and the like, air filtration and air recirculation/conditioning is commonly employed.
Data centers are known to be one of the most energy intensive types of facilities that require controlled atmosphere. A data center is a facility used to host computing systems (e.g., servers) and associated components, such as telecommunications and storage systems. A data center also generally includes redundant or backup power supplies, redundant data communications connections, environmental controls (e.g., air conditioning, fire suppression) and security devices. One environmental control approach provides for obtaining and utilizing outside air (i.e., outdoor air) to cool and to control the temperature of hardware associated with the computing systems of a data center.
However, the outside air cooling approach increases concerns of the presence of gaseous contaminants in data centers caused by the introduction of outside air. For example, pollution in the outside air introduces gaseous contaminants that attack (corrode) copper lines on circuit boards, individual components, or silver based soldering joints. Sulfur-bearing gases such as SO2 and H2S, nitrogen-based gases such as NO and NO2, or reaction with toxic gases such as Cl2 and Br can result in corrosion products being formed. The concentration of these gases are in the range of parts per billion (ppb), however, large temporal variations over the same geographical area can be commonly encountered due to weather, geography and economic activities. The indoor gaseous pollutants can be related to the outdoor gaseous concentration, as more polluted regions will have a higher indoor contamination. Thus, by way of example, for cooper lines on a circuit board, copper-sulfide is formed which creeps over the circuit board and short circuits closely spaced lines. For silver based soldering joints, silver-sulfide is formed which eats away at the silver, causing open circuits. Furthermore, airborne dust is also known to chemically corrode printed circuit board components.
A recent American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) recommendation entitled “Gaseous and Particulate Contamination Guidelines for Data Centers,” August 2009, the disclosure of which is incorporated by reference herein in its entirety, set an upper limit of an acceptable corrosion level in data centers at 30 nanometers per month (nm/month) for both copper and silver.